Apparatus for pulmonary ventilation during anesthesia



F. FRANZ 3,114,365

APPARATUS FOR PULMONARY VENTILATION DURING ANESTHESIA Dec. 17, 1963 4 Sheets-Sheet 1 Filed May 15, 1959 IN VENT OR BY k I ATTORNEYS F. FRANZ 3,114,365

APPARATUS FOR PULMONARY VENTILATION DURING ANESTHESIA Dec. 17, 1963 4 Sheets-Sheet 2 Filed May 15. 1959 INVENT OR WWW ATTORNEYS F. FRANZ Dec. 17, 1963 APPARATUS FOR PULMONARY VENTILATION DURING ANESTHESIA 4 Sheets-Shet 3 Filed May 15. 1959 INVENTOR BY Q2 4 4am ATTORNEY Dec. 17, 1963 F. FRANZ 3,114,365

APPARATUS FOR PULMONARY VENTILATION DURING ANESTHESIA Filed May 15, 1959 4 Sheets-Sheet 4 INV EN TOR fM ATTORNEYS United States Patent 3,114,365 APPARATUS FOR PULMONARY VENTILATIGN DURING ANESTHESIA Frederick Franz, 2 Weodruif St, West Haven, Conn. Filed May 15, 1959, Ser. No. 813,596 16 Claims. (Cl. 128--29) This invention relates to an apparatus for pulmonary ventilation during anesthesia, and more particularly to a device for assisting the patient in his breathing during partial anesthesia and for positively supplying ventilation to the patient when completely narcotized while at the same time supplying to the anesthetist exact information concerning the adequacy of the ventilation of the patient with respect to the three elements referred to below. This application is a continuation in part of my prior application, Serial No. 748,943, filed July 16, 195 8, and now abandoned, having the same title.

The three most important elements that the anesthetist watches for proper ventilation of a patient narcotized under anesthesia are, first, the tidal volume of gases delivered to the patient; second, the number of respirations per minute; and, third, the result which is the product of the first and second element, namely the volume of gas delivered to the patient per minute. The tidal volume is the volume of gas inspired and expired by a patient during each respiration and is usually expressed in cubic centimeters. When tins figure is multiplied by the number of respirations per minute, the product is the volume of gas delivered to the patient expressed in cubic centimeters or liters, and this minute volume of oxygen received by the patient is an indication of the degree of ventilation.

It is usual in anesthetizing a patient for the gases to be supplied manually, by the anesthetist squeezing a bag, to assist the natural breathing of the patient when his natural breathing diminishes. It is proposed by the present invention to perform these functions automatically by power-operated means, the power being furnished by pressure of a gas, preferably oxygen, which may also be delivered to the patient and to supply the anesthetist with the necessary information as to the degree of ventilation of the patient and as to other necessary factors. To this end means is provided for automatically assisting respiration of the patient, particularly during lapse of consciousness and during unconsciousness, so that manual operation of the usual bag will not be necessary. Moreover, the apparatus is operated pneumatically from gas pressure under control of the anesthetist so that the proper ventilation will be administered.

One object of the invention is to provide a new and improved apparatus for ventilating a patient.

A further object of the invention is to provide an apparatus of such a character that it may be automatically operated under control of the needs of the patient.

Still another object of the invention is the provision of an apparatus which will supply gas to the patient during the inspiratory period and withdraw gases from the patient during the expiratory period wherein a switching system is provided to switch from one phase of the action to the other, this system being controlled by an adjustable degree of pressure in the mask covering the patients nasal and oral passages.

Still another object of the invention is to provide an apparatus of the character just described wherein the switching system will be magnetically actuated.

Still another object of the invention is to provide an apparatus of the character described wherein a pump is provided for delivering gas to and removing gas from the lungs of the patient, which pump is actuated by a motor having different pressures for the inspiratory and expiraddl ifihh Patented Dec. 17, 1363 tory phases, thus producing difierent inspiratory and expiratory pressures in the lung.

Still another object of the invention is to provide an apparatus of this character with means for indicating the number of respirations of the patient per minute and of regulating the administration of metabolic oxygen ac cording to the demands of the patient.

To these and other ends the invention consists in the novel features and combinations of parts to be hereinafter described and claimed.

In the accompanying drawings:

FIG. 1 is a diagrammatic view of an apparatus embodying my invention, the apparatus being shown during its inspiratory phase;

FIG. 2 is a similar view of the apparatus, the parts being shown in their positions occupied during the expiratory phase of the apparatus;

FiG. 3 is a diagrammatic view of the apparatus similar to FIG. 1 but showing a modified form of the apparatus; and

FIG. 4 is a diagrammatic view of a modified form of a part of the apparatus shown in FIGS. 1 and 2.

Usually in the present manual method of administering ventilation to a patient during anesthesia, a mask such as shown at It) is placed over the oral and nasal passages of the patient indicated at A, which mask is connected to a breathing bag 11 through a passage which may be controlled by a valve 13. A passage 12 leads into the mask and is divided into the passages 14 and 15 on the delivery side of the breathing bag. In the passage 14 is a canister 16 filled with some absorbent such as soda lime to extract the carbon dioxide from the exhaled gas, while the passage l5 communicates with the anesthetic gases and oxygen supplied by the bottles indicated at 17. The passage 15 is controlled by a check valve 18, permitting gases to pass only in the direction of the arrow when the patient is inspiring and to close upon expiration, while the passage 14 is controlled by the check valve 19 which allows gases to pass from the patient to the canister 16 upon expiration and to close during inspiration. In order to give proper ventilation to the patient, the anesthetist usually operates the breathing bag 11 manually, and the passage 33 leading from the valve 13 is connected directly to the passages 14 and 15.

in the present invention, where it is desired to render the administration of gases to the patient automatically, the breathing bag ll is provided only for emergency use and normally the valve 13 will stand in the position shown in FIG. 1 wherein the bag is cut oft from the apparatus. As I prefer to employ a bacterial barrier in the system, the passages 14 and 15 are connected by a conduit 314 to a collapsible bag 315 in a sealed chamber 316, and the duct 13 leads into this chamber in the space surrounding the bag.

As the valve 13 is open, as shown, the passage 13 communicates with a passage 24? leading to a casing 21 connected by a conduit 22 to a pump comprising a cylinder 23 and piston 24. The actuation of the piston will serve to force gas through the passages 13 20 and 22 in the direction of the arrow, shown in FIG. 1, and to withdraw gas into the pump chamber in the direction of the arrows, shown in FIG. 2. By thus producing pressure and partial vacuum alternately in the chamber 316, the bag 315 will be collapsed and inflated and will thus deliver anesthetizing gas to, and withdraw gas from, the mask 10.

Secured to the piston may be an indicator 25 moving within a transparent housing 26 calibrated, as shown at 2'7, so that the range of movement of the piston 24 is indicated. The tidal volume of the gases transferred to and from the patient on each respiration may thus be read from the scale 27. Connected to the mask It is a conduit 39 to which may be conne ted a gauge 31 to indicate the pressure at the mask, the conduit 39 being connected to a tambour 32 provided with diaphragms 33 and A union or separ ble joint 33 is provided in the conduit 3t and the bag 325 is carried by a flange or cap 317 secured to the chamber by bolts 313 enclosing an opening 333 in the chamber. The opening 319 is sufiiciently large to permit withdrawal of the bag 315. As that part of the system between and including the mask iii and bag 335 and a part of the tube will contain contaminated elements, those parts by the system may be removed for autoclave sterilization by disconnecting the flange 3E7 annd the joint 36a. The tube 3i) is or" such caliber that even at zero oxygen flow through it (as will be hereinafter explained), the positive pressures will never back the gases in the mask into t.e tube 313 for more than a fraction of its length and the natural outward flow of oxygen from the tambour will continually wash the latter and a part of the tube 3%, keeping these elements sterile.

A link connects the diaphragm 33 to a valve member 35 movable within a valve casing 37, this casing being vented to the atmosphere at and 39. A tube it connects an intermediate portion of the casing 37 with a supply of gas under pressure 4-1 which in this instance is oxygen. To the lower end of the valve member 36 is connected an armature 42 acting beween spaced magnets 43 and 44- secured respectively to brackets 45 and as, which brackets are slidably mounted on a support 47, which support is in turn slidably mounted on the member 4-3.

The brackets 45 and 4-6 may be adjusted toward and from each other by the rotation of an adjusting screw provided with rightand ler'thand threads, while the brackets 47 may be adjusted with respect to the bracket 43 by an adjusting screw 59 rotatably secured to the bracket 4-7 and threaded, as shown at 51, into the upper portion of the member It will be noted that the valve member 36 is provided with three spool valves thereon 36, 3S and 36, and a conduit 52 connects the lower portion of the valve casing 37 to a main controlling valve consisting of a casing 53 and a spool valve within said casing comprising valve members 54 54 and 54. Similarly a conduit 52 connects the upper portion of the valve casing 37 with the upper end of the valve casing 53.

The conduit 55 which connects the conduit it to the valve casing 37 is also connected to the valve casing 53 through the passages 56 and 57. Within these conduits are pressure-reducing valves 5'8 and 59 which may be set at any desired value to regulate the pressure of the gas entering the valve casing 53 from the supply 41.

A conduit 6! leads from the lower portion of the casing 53 into the lower portion of the casing 61 of a motor which comprises this casing and a piston d2 connected to the piston 24 previously described by the rod 63. A conduit 6 leads from an upper portion of the casing 53 to the casing 61 above the piston 62 whereby pressure alternately introduced through the passages and 64 will effect upward and downward movement respectively of the piston 62. It may here be noted that the casing 53 is vented to the atmosphere at 65 and 66.

The structure already described may be set forth briefly as follows. When the patient inspires slightly, the diaphragm 33 is drawn into the tambour 32, as shown in PEG. 1, thus raising the valve member 36 to the position shown in this figure whereby the valve 36 permits communication between the passages 4i) and 52, thereby introducing gas under pressure from the tank 41 to the lower end of the valve casing 53. This large valve has sutficient power to switch high pressure gases into the motor 61, 62 so that in the present instance, when pressure enters the lower portion of the chambers 53, the valve therein will be raised to provide connunication between the passage E7 and the 69 leading to the l lower portion of the pump cylinder 61. This drives the piston of the pump upwardly and, by driving the pump upwardly, delivers gases through the duct 22, casing 21 and ducts 29, 15 and 12 to the patient and the anesthetic system comprises the bottles 17.

As the patients lungs become filled, he no longer exerts a negative pressure at the mouth piece or malts 1% but will eventually exert a positive pressure when his lungs are filled. When this occurs, pressure in the line 39 will rise correspondin ly which will be indicated on the gauge and will expand and force downwardly the diaphragm 33 of the tambour 32. This expansion will, however, take place only when the pressure at the mouth piece, and consequently at the tambour, has changed from negative pressure to zero and has built up a positive pressure in the mask. The outward movement of the diaphragm 33 will then move the valve member 35 from the position shown in PEG. 1 to that shown in FIG. 2 under the influence of the magnetic switching pressure control system constituted by the magnets 43 and 44, armature 2 and associated structure.

The armature 42 is attached to the valve member 36 and comes within the combined influence of the upper magnet 4-3 (to which it has been closer than to the magnet 44, it being assumed that the two magnets are of equivalent strength and the lower magnet 44. When the armature 42 is closer to magnet 43 than to magnet 44, as shown in FIG. 1, it will require a predetermined specific force to move it from this position. This force is provided by the pressure exerted by the patient in passage 3i acting through the diaphragm 33. When it is attained, a slight movement of the armature 42 will immediately reduce the pull of the magnet 43 and increase the pull of the magnet 44, thus resulting in rapid and sure switching, more or less of a snap action. When the valve member 36 has been switched to its lower position shown in FIG. 2, connection will be made between the gas supply line 417 and the upper end of valve hous- 53 through the passage 52. The gas will then flow through passage 56 and out of outlet 64- into the cylinder 61 of the motor above the piston 62 and thus pull down the pump piston 24, withdrawing gases from the patient.

The pressure at which the switching from inspiration to expiration takes place can be altered by changing the distance between the magnets 43 and 4-4 by means of the screw 49. If it is desired that the positive switching pressure at the end of the inspiration be greater than the negative switching pressure at the end of expiration, the magnets may be biased, if desired, so that one pulls more than the other by means of the adjusting screw 5% That is to say, the magnets will be moved up or down together so as to place one closer to the armature 42; than the other and may even be biased so far as to produce extremes wherein both will switch upon positive pre sure instead of one positive and the other negative, thus permitting their use in so-called intermittent positive pressure ventilation.

The pressure-reducing valve 53 supplies the gas for the expiratory stroke and the valve 59 supplies the gas for the inspiratory stroke of the apparatus. By altering these pressures the anesthetist can control the time required for a transfer or" a given volume of gas to the patient on inspiration and from the patient on expiration. He can thus regulate the number of respirations per minute.

Leading from the inspiratory outlet 69 is a conduit 70 (it may, if desired, be attached to the expiratory outlet 64) which leads through a passage 71 to a cylinder 72 having a piston '72 movable therein. This piston rod 74 is pivoted to one end of a lever 76, which oscillates about a pivot point "77 and to which is pivoted a pawl 75. The lever '76 is biased in a counterclockwise direction by a spring 73 while the pawl 75 is urged into engagement with a ratchet wheel 7 by a spring 89. Movement of the ratchet wheel in a clockwise direction by upward movement of the piston rod 74 trips a lever 81 pivoted at 32, which lever contacts the crown 83 of a stop watch 8 5.

Gas rushing out of the outlet passage 61} raises the piston 73 so as to move the ratchet wheel one step in a clockwise direction. When the respiration direction changes to expiration, gas is expelled from the outlets 6d and 65, allowing the piston '73 to descend by virtue of the spring '73. When exactly the same starting instant in the next cycle appears, namely, that at which inspiration again starts, piston 73: again rises, clicking the stop watch, and thus indicating one complete cycle of breathing. The stop Watch has a special dial which is calibrated not in seconds but in the number of respirations per minute corresponding to the interval between the starting and stopping of the watch and is of the type in which one pressure on the crown hand stops the hand, allowing the reading to be taken, and the second pressure on the crown performs the functions of both returning the pointer to Zero and instantly starting the watch again.

Since the rate of respiration is the result of the relation between the acting pressures delivered by the reducing valves 58 and 59 to the piston 62 which actuates the pump and the resistance of the circuit to the movement of the pump piston 24, this rate may be adjusted either by changing the pressure delivered to the motor piston 62 or by changing the resistance. The reducing valves 58 and 59 may be adjusted to deliver the proper pressure to the motor, and I have also provided means for adjusting the resistance in the circuit between the pump and the mask of the patient. This is eflected by varying the eflective size of the conduit 22 which may be regulated by a throttle valve in the form of a clamp 22 which has a fixed jaw 22 and a movable jaw 22. The latter is connected to a screw 22 threadedly mounted in the clamp so that it may be adjusted toward and from the fixed jaw 22 of the clamp and restrict the eliective size of the passage 22 as desired.

in order to assist a conscious patient in his inspiration and expiration and to permit wide variations in a conscious patients capricious demands, a butterfly valve 86 is provided in the casing 21, this valve being pivoted at $7 and provided with an arm 88 to which is connected a rod or stem 89 secured to the diaphragm 34 to be moved thereby. A leaf spring 9% may be secured at one end to a fixed member 91 and the other end of this leaf spring is engaged with the rod so as to normally bias the valve 86 toward the position shown in dotted lines in FIG. 1 regardless oi'the direction in which it is moved from this position. This dotted-line position may, therefore, be considered as the normal position of the valve 86, and the amount of gas flowing around the valve is suliicient under the higher pressures of the pump, employed with a conscious patient, to deliver a normal supply of gas to the patient. However, should the patient desire a greater flow as in sighing, for example, (which he does by inspiring and creating a negative pressure at the mouth piece or mask, this negative pressure pulls down the dia phragm 34 of the tambour 32 and deflects the valve 86 into a position shown in full lines in FIG. 1 or a position between the dottedand full-line positions, thus reducing the resistance of the circuit and allowing a greater flowrate of the gases.

The amount of opening of this valve for any given effort of the patient is determined by the stiffness of the spring employed to urge the valve toward its central or zero position, and this in turn controls the rate at which the increased flow of gas is delivered which dir'lers from the usual systems of assisted ventilation wherein the patient receives a fixed flow of gases and receives such flow only on inspiration. In the present system the patient receives gases proportional to the demand during inspiration. and he may also cough or expire if desired without the machine limiting his rate of displacement.

As the patient sinks into deeper and deeper stages of anesthesia, he loses sensitivity to his physiological re- .the pump 23, 24.

flexes of which the breathing reflex is one. The result is that the tidal volume taken by the patient consciously Without assistance decreases from respiration to respiration as also does the number of respirations per minute or the rate of breathing. When the anesthetist sees this stage of breathing approaching, assuming that the ventilation of the patient is becoming inadequate, he increases the pressure delivered by the reducing valves 58 and 59 to increase the assistance to the patient. A comparable result may be secured by increasing the switching pressures by the adjustment of the magnets 43 and 44. When the patient finally reaches the stage of apnea, the stage in which his voluntary breathing has completely stopped, it may be desirable to hold the valve 86 in an open position. For this purpose a tumbler lever 92 is pivoted at 93 adjacent the diaphragm 34 so that it may be moved from its full-line to dotted-line position shown in FIG. 1 to push downwardly the diaphragm 34. The valves 58 and 55* can then be adjusted to reduce the pressure of the gas delivered thereby and also the switching pressures may be adjusted by adjustment of the magnets 43 and 44 until the apneaed patient no longer breathing voluntarily receives adequate ventilation as determined by the anesthetist.

When the patient is in this condition gases are delivered during the inspiratory phase until the chest is expanded to that point in which the valve member 36 is tripped or switched by the cooperative action of the mask pressure on the diaphragm 33 and the magnets 43 and 44 acting on the armature 42. Then the patient expires owing to the attempt of the recoil forces in his chest to assume the relaxed position aided by the expiratory suction of When the negative pressure at the end of expiration is attained, having been produced by the action of the pump 23, 24 in drawing air out of the patients lungs, the valve member 36, by virtue of diaphragm 33, in combination with the magnets 43 and 44, reverses to the inspiration phase and thus the cycle is repeated.

It is obvious from the foregoing that the motor and the pump piston 24 follow a reciprocatory motion, alternately inspiring and expiring the patient either in conformity with his desires or at a regular rate when he has entered apnea. The amplitude of this reciprocation of the piston rod 63 is only a fraction of the total available amplitude of the pump. As long as the oxygen being delivered to the patient is equal to the consumption by the patient in converting his venous blood into arterial blood, the excursions of the pump piston will be through the same range and the same zone. If, however, the metabolic consumption is greater than that being delivered to him, the successive excursions of the pump piston 63 will gradually approach the top end of the pump, at which point no more gases would be available in the pump chamber. If, on the other hand, the consumption of gas is less than that delivered to the patient, the excursions will gradually go in the other direction.

In order to eliminate the necessity on the part of the anesthetist for watching the amount of gas in the system, means is provided to automatically deliver oxygen from the supply 41 to the breathing mask. A conduit 95 controlled by a reducing valve 96 leads from the tank 41 to the orifice 97 of a metabolic regulator comprising a chamber E98 and piston 99. Connected to the piston is a metering pin or needle valve 100 which controls the orifice 97 and thus controls the entrance of gas into the chamber A conduit 101 leads from this chamber through a flow meter 192 to the tambour 32 and thence through the line 3% into the mask 10. A lever 103 pivoted at 1% has one end engaged with the. piston 99 and the other end of this lever is adapted to be engaged by pins and 1% on the piston rod 63 so that the metering valve 1% will be automatically opened and closed in the event that the excursions of the piston carry the rod to extreme upper and lower positions.

In the event that the patient consumes more oxygen than is being fed to him and the piston 63 moves upwardly, the pin 105 will gradually move the adjacent end of the lever 193 upwardly and thus open the metering pin an amount sufiicient to permit a greater quantity of oxygen to fiow to the patient to balance his consumption. if too much has been fed out and the patient does not consume as much as is delivered to him, the piston 63 will gradually reciprocate further and further at the lower range of its stroke until the pin 1% engages the lever 163 and moves the metering pin 1% upwardly to close the orifice 97. Eventually a balanced position will be assumed by the metering pin corresponding to the metabolic consumption of the patient.

The position of the parts of the apparatus during the expiratory phase is shown in FIG. 2 and the movement to this position may now be described. It has already been explained that during the inhalation of a conscious or semi-conscious patient a partial vacuum is created in the tambour 32, thus opening the valve 86 to the position shown in full lines in PEG. 1 against the bias of the spring 91 As the inspiratory phase approaches the patients full capacity, the latter no longer creates a par tial vacuum in the system, and the valve 86 gradually moves toward its dotted-line position shown in this figure. However, the magnet has been set by the anesthetist to effect the switching of the valve member 36 at a definite positive pressure determined by him as being that necessary for switching when the lungs are filled with an adequate volume of gas, and the change in the position of this valve will not be effected until this point has been reached. It will be noted, however, that when the patient stops breathing when hi lungs are full, the mask pressure goes from negative to zero and then to position as the gases continue to be delivered by the pump. It is desirable, therefore, to provide means for preventing movement of the valve past its dotted-line position shown in FIG. 1 so as to prevent a great, though temporary, inrush of air at the end of the inspiratory phase when conditions should be more tranquil.

To this end a stop lever 167 is pivoted at 1118 adjacent the casing 21 so that the lower face of this lever may be held by a spring 1119 in position to engage the pivot pin 110 by which the arm 88 is pivoted to the rod 89.

Similarly a lever 111 is pivoted at 112 and biased by the spring 113 in position to engage the pivot 110 when the latter is in its upper position shown in PEG. 2. The levers 107 and 111 are provided with arms 115 and 116 adapted to be engaged by pins 117 and 118 on a piston rod 119. Upon the upper end of this rod is a piston 120 moving in a cylinder 121 to which gas is delivered by a conduit 122 connected to the conduit 71 Similarly, the lower end of the piston rod 119 carries a piston 123 in a cylinder 124 to which gas is delivered by the conduit 125 connected to the conduit 64. Fixed stops 126 and 127 may be provided to engage the lever arms 115 and 116 so as to limit the movement of these levers by the springs 1G9 and 113.

It will be noted that, as shown in FIG. 1, the end of the lever 111 is out of the path of the pivot 11%, thus permitting the patient to inspire at any variable rate as it allows the pin 119 and, therefore, the valve 26 to assume any position it chooses during this inspiratory period. However, when the switch over to the expiratory phase takes place and the patient has finally received the necessary air during the inspiratory phase, expiratory air will be delivered from the valve housing 53 through the passage 64 to the chamber 61 of the motor above the piston to draw the pump piston downwardly. Simultaneously air will be delivered through the passage 125 to the cylinder 12 i below the piston 123, moving the latter upwardly to the position shown in 1 16. 2.

The pin 118 is, therefore, moved away from the tail 116 of the lever 111 and the spring 113 is allowed to pull the lever 111 in a clockwise direction into the path of the pivot pin 1141, thus preventing the valve 86 from again returning past its neutral position to a position which it would occupy in the inspiratory phase of the apparatus. Simultaneously the tail of the lever 167 is engaged by the pin 127 and this lever will be moved against the action of the spring 109 into the position shown in FIG. 2 in which its lower face is out of the path of the pivot pin 11%. The apparatus is now in the expiratory phase.

With the elements in this position, the patient expires and positive pressure in line 30 will lift the valve as to the position shown in FiG. 2 or any position on that side of its neutral position which satisfies the expiratory demands or rates. If during this period the patient should temporarily arrest his expiration, bringing the masl; pressure to zero and even slightly negative but not negative enough to switch the valve member 36, the pin 110 would be blocked by the lever 111, thus again preventing the valve 86 from being moved to the other side of its neutral position and again preventing an exorbitant rush of air near the end of the expiratory stroke at the time when tranquility would be desired and before the apparatus is shifted to the inspiratory phase by the valve member 35.

In FIG. 3 of the drawings I have shown a diagrammatic view of an apparatus generally similar to that described above but differing in certain details, some of which are in addition to the features of FEGS. l and 2 and others are substituted for certain of the mechanisms previously described. The various parts of the apparatus shown in FIG. 3, which are the same as those previously described, will be given the same reference charesters and, as their function is the same in the present modification, it will be unnecessary to further describe those features and their functions.

in some instances if the patient should take a very deep breath and empty the breathing bag 315' or should the mask for any reason he removed from the patients face while the bag is in the emptying phase, it may be that there would be an inadequate supply of gas in the bag to give the patient all he needs. Therefore, mechanism such as a flood valve is provided to supply a practically unlimited quantity of oxygen to the mask. For this purpose a follower 13%} is provided upon the end of a lever 131 pivoted at 132 to the wall of the chamber 316, this follower being urged against the bag 315 by the spring 133. The lower end of the lever 131 is connected to a plunger slidably mounted in a valve house 135. This chamber is provided with a passage 136 controlled by the valve 137. The passage 136 provides communication between the chambers 133 and 139 in the valve housing 135 and the chamber 138 is connected with the oxygen supply 11 by the conduit 14%).

The chamber 139 is connected to the bag 315 by the conduit 141. The follower 13%) serves as a detector and, as the bag approaches its empty or collapsed position, the follower will be moved toward the left, as shown in FIG. 3, by the spring 133 which moves the plunger or spool 13 1 to the right, as shown in this figure, carrying with it the valve 137, and thus permits oxygen to pass from the chamber 138 through the passage 136 into the chamber 13%, and thence into the bag 315 to replenish the supply of gas. As soon as the bag fills the plunger 13 will be moved toward the left and cuts off the supply of oxygen through the passage 136. In this way there is always an adequate supply of oxygen in the bag 315 to satisfy the demands of the patient as the supply is autom...ically maintained as described in response to an inordinate collapse of the bag 315.

It may sometimes occur that at the expiratory end of he patients respiration the bag will become too full or too far extended. This may occur if for some reason the patient expires a more exorbitant or excessive amount or if the patient should begin expiration when the bag is nearly full. Means is, therefore, provided to automatically vent any such excess from the bag.

To this end a vent opening 143 is provided for the bag which in this instance is located in the conduit 14-1. This opening is normally covered by a flap member 144 pivoted at 145 and normally closing the vent opening .143. The nose of a lever 14d pivoted at 147 bears upon the flap 1 M and holds it in closed position under the influence of a toggle mechanism formed by the link 14% and a bell-crank lever 14-9, the lower arm of which is held against a stop by the spring 151, in which position the flap 144 is closed. The other arm of the bell-crank lever is pivotally connected by a link 152 to a lever 153 pivoted at 154 and having one end 155 standing in the path or" a pin 156 on the piston rod 53 of the pump, which pump as previously explained comprises the cylinder 23 and piston 24.

As long as the piston 63 is reciprocating over its normal range, the pin 156 does not contact the end 155 of the lever 153, and hence the flap 144 remains closed and gas is not vented from the bag 315. If, however, the bag should become too full, which means that the pump chamber 2 3 has become too full, the pin 15 6 strikes the lever end 155 and moves it downwardly, thus swinging the bell-crank lever 149 in a clockwise direction and permitting the flap 144 to uncover the vent opening 143, thus allowing any additional gas expired by the patient to escape from the bag 315 beneath the flap.

The slightest attempt of the patient to inhale at any time reduces the pressure in the line and reverses the diection of the movement of the pump piston 24 and piston rod 6 3, and thus raises the pin 156 from engagement with the lever end 155 and permits the flap 14-4 to be closed by the action of spring 151 on the bell-crank lever 149.

in the embodiment of my invention previously described means is provided comprising the needle valve ill-ti and associated structure to automatically deliver oxygen from the supply to the breathing mask to satisfy the metabolic consumption of the patient so as to eliminate the necessity on the part of the anesthetist for watching the amount of gas in the system. An alternative means for this purpose is provided in the modification of my invention shown in FIG. 3 and will now be described.

A conduit 153 leads from the oxygen supply 41 to the chamber 159 of a valve housing 150. The communication between this chamber and a chamber 161 of larger diameter in the housing 16G is controlled by a valve member 162, this valve having a slight clearance in the chamber 159 which joins the chamber 161 by a shoulder 163.

The valve 162 is connected by a U-shaped link 164 to the flood valve 134 by means of a lost-motion connection. The valve 137 is provided with an extension 165 having an elongated slot 166 therein and an end 167 of the link 1:34 is movably engaged in this slot.

With this construction normal collapsing and expanding movements of the bag 3115 and of the pump piston 63 are allowed without disturbing the quantity of metabolic oxygen delivered to the patient as normal movements of the valve 137 will not disturb the position of the link 164 and valve 162. However, should the patient demand more oxygen than that being fed to him for any cause by the apparatus, the bag 315 would collapse or decrease in size to such an extent that the follower 130- would make excursions closer to the center line of the chamber 316 and, as the valve 137 would then be moved farther to the right, the link 1164 would be repeatedly urged in this direction, pushing the valve 162 closer to the orifice of the passage 159, thus allowing an increasing amount of metabolic oxygen to pass through the clearance between the valve 162 and the chamber 15% into the chamber 161. From this chamber the oxygen passes through the conduit 16 9, through the flow meter 1102 to the tambour 32, and thus to the mask through the conduit 3%.

Since it is extremely difficult to make the joint between the walls of the piston 24 and cylinder 23 air tight or proof against gas leakage, means is provided in the pres ent modification for supplying additional gas to the system to compensate for this leakage. To this end the oxygen supply 41 is connected by a conduit 170 to a chamber 171 in a valve housing 172 under control of a needle valve 173. The chamber 171 communicates with the cylinder 23 above the piston 24 by conduit 174.

The needle valve 173 is connected by a link 175 to an arm 176 of a lever pivoted at 177, the other arm of which is forked so as to provide two spaced members 178 and 179. A pin 18% on the piston 63 is disposed between the spaced ends 178 and 179 of this lever.

During inspiration the pressure in the pump chamber 2-3 above the piston 24 is positive so as to force the gases through the circuit and into the lungs while during the expiratory phase this pressure is negative. However, the dilierence between this positive pressure and ambient pressure is greater than the difierence between the negative pressure and ambient pressure and as a result gas in the chamber 316 and the connecting conduits progressively leaks out to the atmosphere and the pump piston gradually approaches the closed or bottom end (upper as shown in the drawing) of the cylinder 23 in its range of movement until it is stopped and can no longer deliver gases.

Just before this occurs the pin 18% strikes the end 178 of the lever and opens the needle valve, thus permitting oxygen to enter the system including the pump chamber above the piston 24 and the bag chamber 316. The distance between the lever ends 178 and 179 is sufficiently great to allow normal excursions of the pin 180 due to exchange of tidal volume of gas without disturbing the position of the needle valve 173. As soon, however, as the piston progressively changes the position of its stroke, the needle valve is moved by small increments until the losses from the chambers 23 and 316 equal the gas supplied by the needle valve. This prevcnts the piston from bottoming in the pump which would result in serious impainnent of its function.

In the modification of the invention which is presently being described, there is provided an alternative method for controlling the number of respirations per minute. When the pressure at the mouth of the patient is zero, the two diaphragms in the tambour 32 are in a neutral position, the upper one 34 being so shown in dotted lines in FIG. 3, and the butterfly valve 86 is in neutral position, as shown in dotted lines in this figure, offering its greatest resistance to the flow of ventilating air past this valve. It is understood that there is always clearance between this valve and the casing 21 so as to permit a minimum flow through the casing. If the patient should become apneaed and make no effort to inspire or expire, the diaphragm 34 would not be either sucked down or pushed up because the pressure from the mask entering through the duct 30' would not vary. However, owing to the small how of gas past the butterfly valve in its neutral or closed position, the anesthetic gases and oxygen will be delivered to and extracted from the lungs of the patient but at a lower rate which will be indicated on the graphic chart drawn by this instrument.

However, if at any time the anestheologist desires to increase the rate of respiration, a by-pass 182 is provided about the valve 86, this by-pass being controlled by a mmually operated valve 183, which by-pass may allow more gas to pass to the chamber 316 and consequently increases the rate of respiration because the chest is filled more rapidly and, therefore, switching pressure to change the stroke of the pump is attained or reached earlier.

Under normal breathing and at the end of inspiration with gases delivered from the apparatus, the chest becomes filled and the switching pressure required to switch the apparatus from inspiration to expiration is reached, thus tripping the mechanism from the inspiratory to the expiratory stroke. The chest muscles, having been expanded, new contract, and, in attempting to expell the gases, create a pressure at the mouth. "this pressure is tra remitted through the tube to the tambour 32. Under influence of this pressure diaphragm 34 expands and opens the valve 36 by moving it beyond the dotted-line position shown in KG. 3. This allows the gas to escape from the chest to the pump at a rapid rate past the open valve 86. As soon as pressure at the mouth decreases wing to the escape of gases from the lun s, the pressure on diaphragm 34 decreases, the latter collapses, and the valve so closes or returns to its neutral position, shown in dotted lines in HS. 3, thus reducing the rate of flow.

This rapid expelling of the gases immediately following the end of expiration produces a rapid drop in the pressure in the pulmonary system and thus avoids obstruction of cardiac output. This rapid drop of pressure is referred to as the Cournand curve in an expiratory phase.

One result of this rapid expelling of the gases at the beginning of expiration is that the duration of expiratory time is decreased. In order to bring this time into a more normal relation to the natural inspiratory time a structure is provided which will now be described.

A control lever 1.34 is pivoted at 185 and urged by a spring 186 downwardly against a stop F 7. The free end '88 of this member straddles the link and bears against a member 1% on the upper diaphragm 34 when the latter is in its neutral position as it is when ambient pressure is present in the tarnbour 32. With negative pressure in the tambour the diaphragm 3 is pulled away from the member 185, as shown in full lines in FIG. 3. With positive pressure (such as is present at the beginning of expiration) in the tambo-ur 32, the diaphragm rises and raises the lever 18d against the action of the spring 336 to the dotted-line position shown in FIG. 3.

The tension of the spring is so chosen [that the lever 18% will be lifted at the beginning oi expiration, thus opening valve 85 and allowin the gas to escape from the mask rapidly but the tension gradient of the spring 185 is such that as soon as gas pressure drops, the lever 18?- overcomes the remaining pressure of the expiratory gases at the mouth of the patient and forces the diaphragm inwardly to close the valve 85. or move it to its neutral position. This results in the rapid drop of expiratory pressure at the be ning of expiration and yet retards the flow of gas durlng the middle of the expiration, permitting a more normal length or" expiratory time.

If use of the lever 13-4 is not desired, this member may be moved to an inoperative position by a ct n member 191 rotatably mounted below the lever and rotated by a handle 1: 2 which cams the lever to its inoperative dotted-line position shown in PEG. 3 where it will no longer engage the member 1% even at the greatest expansion of the diaphragm 3 2.

In the form of the invention shown in FIGS. 1 and 2, the members 25, 2d and 27 provide means for recording or indicating the tidal volume of gas delivered by the pump. This mechanism has some limi 'ons, however, which it may be desirable to avoid in that it does not take into consideration the difference in pressure which obtains in the system or the pump cylinder during the operation of the mechanism.

The exact volume of in the system naturally de pends upon the positive and negative pressures employed during the inspiratory and expiratory phases. The pump pressure in the present apparatus is positive during an inspiratcry phase and negative during an expiratory phase with relation to ambient pr me so that the absolute pressure is greater during the former phase than during the latter. The gas in the s stem is, therefore, alt rnately subjected to these absolute pressures, and it will be recognized that according to Boyles law the change of volume of the can readily be computed for any change in pressure.

Since it is desired to record the tidal volume of gas delivered to the patient by the pump in each cycle, there must be compensation for the volume moved by the pump piston in merely compressing the gases, by subtracting the volume corresponding to compression on the one hand or rareiication on the o her hand from the total volume moved by the piston in order to obtain the actual volume deliver (1 to the atient d 'ing insoiration and extracted from him during expiration. In other words, a part only of the movement of the pump is effective in deli ering gas to or drawing it from the patient, the rema rdcr being etiective to compress or rarely the gas. This compensation is effected automatically by the linkage employed in the present apparatus which will now be described.

pump and to the other end or"; this linl' is pivoted one end of a lever 1%. The other end of the lever 19-5 is pivot d to a hr. 197, the other end of which is pivoted at to a lever 1B, which lever is pivoted by a pivot pin 2% to a fixed member 261. The lever 199 is provided with an elongated slot 2% to receive the pivot pin 2% so that the lever 199 may move to some extent with respect to the fixture The lever 1% is pivoted at to one arm of a bell-crank lever pivoted at 2-35 to a fixture 23d and the other arm 2 of this bell-crank lever is connected to a link which carries a stylus 253' adapted to record movements of the lever upon a c S.

If the end 13 6 of the lever 196 were pivoted to a fixed part of the 2" tratus, it will be seen that me e cuts of the piston wotnd be recorded on the chart but on a reduced so ie, and the chant could be calibrated to show the volume displaced by the piston. This would, of course, be greater than the volume delivered to the patient by an amount equal to the elastic compression of the gas, that is, by the volume displaced by the piston in changing the pressure of the gas without deli ering any to or withdrnv rig any from the patient.

Instead, however, of being pivoted to a fixed point on the frame, this end of the lever arm 1% is connected to one end of the lever 199, the other end of which is pivoted at 211 to a collar or sleeve 222 frictionaliy but slidably mounted on the piston rod 63. ltiovement of the collar 212 with the piston rod is limited by the arms 233 and 214 provided upon a U-shaped jaw member 215 and secured to a fixed part of the apparatus.

With this construction, as the piston rod 63 recip cates, it carries with it the collar 222 for a distance eq to the clearance between it and the arms 213 and a distance equal to that indicated at 216. The levers l and 199 being of similar dimensions, the distance 2.6 will be the lost motion or compensation for the change in volume of the gas in the system due to its compression or rarefication. For example, as the piston rod 63 moves downwardly from the position shown in FIG. 3, it will be seen that until the collar 212 strikes the lower arm 214 of the jaw member 215, the adjacent ends of the levers 1% and 299 will move together with the position of the bellcrank lever 266, 287 will not be affected. So soon, however, as the collar Z12 is held against movement, the end 1% of the lever 1% will serve as 21 {ulcrum in any further movement of the piston 63 and a record will be made upon the chart 2.15.

As shown in the drawing, it may be assumed that the piston rod 63 has risen or moved inwardly with respect to the cylinder 23 until the sleeve 212 has come into contact with the stop 213 which will prevent further movement of this sleeve. Sin-cc the lovers 1% and 199 are of identical dimensions, the point 233 will not have moved and hence the bell-crank lever 235, will not have been moved. Therefore, there wil be no movement of the stylus 2&9. :Iowevcr, upon continued upward movement of the piston 63, as the movement of the sleeve 25?. will have been arrested and the inner end of the lever will continue its movement due to its connection to the piston rod through the link 1M, the pivot point 2% wiil move relatively to the pivot pin it?!) and thus rotate the bellcrank lever in a clockwise direction, thus recording the actual delivery of gas on the chart 21%. It is only necessary to choose the distance 216 to agree with the change of volume corresponding to the range of gas pressure in the system to eflfeot compensation for the volume change on the record made upon the chart.

The use of the container 316 and the collapsible bag 315 is principally to provide a bacterial barrier between the part of the apparatus associated with the mask and the remainder. If such a bacterial separation of the parts of the apparatus is not required, the collapsible bag may be dispensed with. Such a construction is shown in FIG. 4 of the drawings which shows a portion of the apparatus adjacent the mask. In order to avoid repetition, the remainder of the apparatus is not illustrated but it is understood will be employed.

As shown in FIG. 4 the mask is connected by the passage 12 to the passages 14 and 15. The passage 14 leads through a canister 16 filled with an absorbent to extract the carbon dioxide from the exhaled gas while the passage communicates with anesthetic gases and oxygen supplied by the bottles indicated at 17.

Both of the passages 14 and 15 are connected directly to the passage 20 which leads to the casing 21 connected to the pump (not shown in this figure) by the conduit 22. If desired a breathing bag 11 may be connected in the passage 24) by the valve 13. It will be understood that as before this breathing bag is provided only for emergency use and, therefore, the valve 13 will usually stand in the position shown in FIG. 4 wherein the bag 11 is cut oil? from the apparatus.

In connection with this embodiment of the invention it will be seen that the positive and negative pressures supplied by the pump and occurring in the housing 21 and conduit 29 will be applied directly to the mask 10 through the passages 14 and 15 to effect the pulmonary ventilation. The result will be the same as that when the collapsible bag 315 is employed except that there will be no bacterial separation of the parts of the apparatus adjacent the mask from the remainder thereof.

While I have shown and described some embodiments of my invention, it will be understood that it is not to be limited to all of the details shown, but is capable of modification and variation within the spirit of the invention and within the scope of the claims.

What I claim is:

1. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to, and withdrawing it from, said mask, comprising a reciprocating piston, an additional source of gas supply under pressure, a motor for actuating said piston, said motor being actuated by gas pressure delivered to it from said additional source, and valve means to control the delivery of the gas under pressure to said motor, means responsive to pressure in the mask and connected to the valve means to actuate the same, and means including a magnet and an armature attracted by said magnet and connected to said valve means for actuating the latter.

2. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to, and withdrawing it from, said mask, comprising a reciprocating piston, an additional source of gas supply under pressure, a motor for actuating said piston, said motor being actuated by gas pressure delivered to it from said additional source, valve means to control the delivery of the gas under pressure to said motor, means responsive to pressure in the mask and connected to the valve means to actuate the same, a magnet for actuating said valve means, and an armature connected to the valve means and moved toward said magnet by pressure in said mask for initiating actuation of said magnetic means.

3. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to, and withdrawing it from, said mask, comprising a pump having a cylinder and a piston reciprocating therein, a conduit leading from said pump to the mask, a movable valve in said conduit to control the passage of gas therethrough, means responsive to pressure in said mask to control the position of said valve, operating means for the pump, means to limit the movement of said valve, and said last-named means being connected to the pump-operating means to be controlled thereby.

4. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to, and withdrawing it from, said mask, comprising a pump, fluid pressure means for operating the pump and a conduit leading from the pump to said mask, a valve in said conduit, means for pivotally mounting said valve for movement to either side of a neutral position, movably mounted stop members adapted to be moved into the path of a part of said valve to limit movement thereof, and means connected to said fluid pressure means for moving said stop members.

5. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to, and withdrawing it from, said mask, said means comprising a pump having a reciprocating plunger, a motor for actuating said pump, said motor comprising a piston, a cylinder, a source of fluid pressure, and valve means for connecting said source with the cylinder on one or the other side of the piston alternately, timing means for indicating the time interval between reciprocations of the plunger, fluid pressure means for actuating said timing means, and means connecting said fluid pressure means with said valve means to be controlled thereby.

6. An apparatus for pulmonary ventilation comprising a mask, a supply source of anesthetic gas, means in asso ciation with said source for delivering gas to, and withdrawing it from, said mask, comprising pump means and a conduit leading from said pump means toward said mask, a regulatable valve for gradually varying the resistance of said conduit to flow of gas therethrough, but always permitting a predetermined flow, and means responsive to pressure in the mask for varying the position of said valve from wide open position to a substantially clgsed position where said predetermined flow is permitte 7. An apparatus for pulmonary ventilation comprising a mask, a supply source of anesthetic gas, fluid-pressureactuated means in association with said source for delivering the gas to, and withdrawing it from, the mask, means to deliver fluid pressure to said fiuid-pressure-actuated means comprising a pump and a conduit leading from said pump to said means, and a regulatable valve for varying the resistance of said conduit to flow of gas therethrough, but always permitting a predetermined flow past said valve, and means responsive to pressure in the mask for varying the position of the valve from wide open position to a substantially closed position.

8. An apparatus for pulmonary ventilation comprising a mask, a collapsible gas bag connected to said mask, mechanism for delivering gas to said mask and withdrawing it therefrom comprising a conduit leading to said bag to collapse and expand the same, means for alternately supplying a gas under positive and negative pressures to said conduit, a valve in said conduit to control the passage of gas therethrough, a diaphragm, one side of which is exposed to gas pressure obtaining in the mask, and means connecting said diaphragm to the valve to open the latter in response to pressure in the mask.

9. An apparatus for pulmonary ventilation comprising a mask, a collapsible gas bag connected to said mask,

mechanism for delivering gas to said mask and Withdrawing it therefrom comprising a conduit leading to said bag to collapse and expand the same, means for alternately supplying a gas under positive and negative pressures to said conduit, a valve in said conduit to control the passage of gas therethrough, a diaphragm, one side of which is exposed to gas pressure obtaining in the mask, means connecting said diaphragm to the valve to open the latter in response to pressure in the mask, and spring means applying pressure to said valve when in open position to move it toward closed position after it has been opened by said mask pressure.

10. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to, and withdrawing it from, said mask, including a reciprocable piston, means for indicating the volume displacement of said piston, and a lost-motion connection between said indicating means and the piston to compensate for change of volume in the gas due to compression or rarefication thereof by movements of the piston.

11. An apparatus for pulmonary ventilation comprising a mask, a collapsible bag in association with the mask, a source of oxygen supply, means affording communication between said supply and the mask, a valve controlling said communication, but permitting a predetermined flow of oxygen therepast at all times, and means responsive to the collapse of the bag for moving said valve to position to increase said flow as the oxygen in said bag is diminished.

12. An apparatus for pulmonary ventilation comprisiag a mask, a collapsible bag in association with the mask, a source of oxygen supply, means affording communication between said supply and the mask, a valve controlling said communication, but permitting a predetermined iiow of oxygen therepast at all times, and means responsive to the collapse of the bag for moving said valve to position to increase said flow as the oxygen in said bag is diminished, and a second valve to supply a relatively large supply of oxygen to said mask in the event of substantial exhaustion of oxygen therein.

13. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to and withdrawing it from said mask comprising a conduit leading from said supply means to the mask, a movable valve in said conduit to control the passage of gas therethrough, means responsive to pressure in the mask to control the position of said valve, phase-changing mechanism for changing said first means from the delivery phase to its With drawal phase, means to limit movement of said valve,

and said last-named means being connected to the phasechanging mechanism to be controlled thereby.

14-. An apparatus for pulmonary ventilation comprising a mask, a gas supply source, means in association with said source for delivering a gas to and withdrawing it from said mask comprising a conduit leading from said supply means to the mask, a valve in said conduit, means for pivotally mounting said valve for movement to either side of a neutral position, movably mounted stop members adapted to be moved into the path of a part of said valve to limit movement thereof, phase-changing mechanism for changing said first-named means from its delivery phase to its withdrawal phase, and means connected to said phase-changing mechanism for moving said stop members.

15. An apparatus for pulmonary ventilation comprising a mask, a supply source of anesthetic gas, means in association with said source for delivering gas to and withdrawing it from said mask comprising a conduit leading from said source toward the mask, a regulatable valve for gradually varying the resistance of said conduit to flow of gas therethrough but always permitting a predetermined flow, and means responsive to pressure in the mask for varying the position of said valve from wide open position to a substantially closed position where said predetermined flow is permitted.

16. An apparatus for pulmonary ventilation compri ing a mask, a system for delivering gas to, and withdrawing it from, the mask comprising a source of gas supply under pressure, a conduit leading from said source to the mask, a regulatable valve for varying the resistance of said conduit to the flow of gas therethrough, but always permitting a predetermined flow past said valve, and means responsive to pressure in the mask for varying the position or" the valve from wide open position to a substantially closed position.

References Cited in the file of this patent UNITED STATES PATENTS 1,983,670 Goodner Jan. 10, 1933 2,180,057 Jones Nov. 14, 1939 2,284,964 Mautz June 2, 1942 2,582,210 Stanton Jan. 8, 1952 2,736,331 S-celer Feb. 28, 1956 2,737,176 Fox Mar. 6, 1956 2,737,178 Fox Mar. 6, 1956 2,880,719 Andreasen Apr. 7, 1959 FOREIGN PATENTS 695,586 Great Britain Aug. 12, 1953 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,114,365 December 1'7, 1963 Frederick Franz It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 24, for "element read elements column 3, line 12, for "those parts by" read these parts of line 14, for "annd" read and line 73, for "chambers" read chamber column 4, line 5, for "comprises" read comprising line 7, for "maks read mask line 69, for "piston 72" read piston 73 same line 69, for "This" read The column 9, line 67, for "farther" read further column 12, line 59, for "with" read and column 16, line 40, for "1,983,670"

read 1,893,670

Signed and sealed this 2nd day of June 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Allesting Officer Commissioner of Patents 

1. AN APPARATUS FOR PULMONARY VENTILATION COMPRISING A MASK, A GAS SUPPLY SOURCE, MEANS IN ASSOCIATION WITH SAID SOURCE FOR DELIVERING A GAS TO, AND WITHDRAWING IT FROM, SAID MASK, COMPRISING A RECIPROCATING PISTON, AN ADDITIONAL SOURCE OF GAS SUPPLY UNDER PRESSURE, A MOTOR FOR ACTUATING SAID PISTON, SAID MOTOR BEING ACTUATED BY GAS PRESSURE DELIVERED TO IT FROM SAID ADDITIONAL SOURCE, AND VALVE MEANS TO CONTROL THE DELIVERY OF THE GAS UNDER PRESSURE TO SAID MOTOR, MEANS RESPONSIVE TO PRESSURE IN THE MASK AND CONNECTED TO THE VALVE MEANS TO ACTUATE THE SAME, AND MEANS INCLUDING A MAGNET AND AN ARMATURE ATTRACTED BY SAID MAGNET AND CONNECTED TO SAID VALVE MEANS FOR ACTUATING THE LATTER. 